Method and apparatus for grinding peripheral grooves in rolling mill guide rollers

ABSTRACT

The present invention relates to a method for grinding grooves in the peripheral surface of rollers roller guides for rolling mills. The roller (2) of a roller guide is caused to rotate while retained on its own bearing (8,9,10) as the peripheral groove is ground. 
     The invention also relates to an apparatus for carrying out the method, and to a roller guide structure with which the method can be applied.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and to a device for grindingthe rollers of rolling mill roller-guides, and a roller guide whichenables the method to be carried out.

2. Description of the Related Art

High demands are placed on the bearings of guide rollers of the kindwhich function to guide rolled metal in between the rolls of a rollingmill, with the intention of preventing a bearing fracture that wouldinterrupt continuity in production. Ideally, the guide bearings willhave the same useful life span as the mill rolls. This aim has not beenachieved in practice, despite endeavors to eliminate play in thebearings and to prevent bias loads acting thereon, by using prestressedprecision bearings which are press-fitted into their respective bearingsurfaces. This problem is particularly accentuated in modern rollingmills in which rolling speeds will reach 100 m/sec, and particularly inthe final stage of the rolling mill where the guide rollers are requiredto rotate at very high speeds. The useful life span of present dayroller guide bearings is not sufficiently long to permit still higherrolling speeds and the higher loads on the mill guide rollers that areoccasioned by these higher rolling speeds.

The object of the present invention is to increase the life span ofroller guide bearings in rolling mills.

SUMMARY OF THE INVENTION

According to the present invention this object is achieved with a methodof grinding circumferential grooves in the roller-guide rollers ofrolling mills, characterized in that the guide rollers are caused torotate in their own bearings while grinding a groove. In this way, thegroove formed in the roller will always lie precisely at right angles tothe rotational axis of the roller and the rolled metal will moveprecisely in the rolling line.

The invention also relates to a device for carrying out the method, saiddevice being characterized in that it includes a carrier which supportsa roller-guide roller and its bearing such as to enable the roller torotate freely in its bearing, a grinding tool which is movable in aradial direction relative to a roller supported by the carrier, andmeans for rotating the roller.

BRIEF DESCRIPTION OF THE DRAWINGS

A roller guide constructed in accordance with the invention ischaracterized in that the roller-guide roller and its bearing are builttogether to form a unit which can be readily detached from the remainderof the guide.

An exemplifying embodiment of the invention will now be described inmore detail with reference to the accompanying drawings, in which

FIG. 1 illustrates from above one embodiment of an inventive rollerguide;

FIG. 2 is a front view of the guide shown in FIG. 1;

FIG. 3 is a sectional view taken on the line III--III in FIG. 1;

FIG. 4 illustrates the roller and the roller bearing of a roller guideaccording to FIG. 3; and

FIG. 5 illustrates schematically an embodiment of an inventive devicefor grinding grooves in the roller illustrated in FIGS. 1-4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 4 illustrate a roller guide for rolling mills, said guidebeing constructed to permit the inventive grinding method to be applied.The roller guide includes conventionally two circumferentially groovedand rotatable rollers 1 and 2 which guide rolled material 3 (see FIG. 2)therebetween in a metal rolling operation. The rollers 1 and 2 arecarried by arms 4, 5, which are in turn carried by a holder 6.

In accordance with the invention, the rollers 1, 2 and their respectivejournals or bearings have the form of units 7 which can be readilyattached to and removed from the arms 4, 5. FIG. 4 is an exploded viewof one such unit 7. In addition to the roller 2, this unit also includesan attachment sleeve 8, a bearing shaft 9 and a bearing part 10 which iscomprised of two pairs of angle contact bearings 11, 12 which areseparated by two co-ground spacing rings 13 which are intended to imparta suitable axial bias to the bearings. As best seen from FIG. 3, thebearing part 10 is press-fitted into a seating means 14 in theattachment sleeve 8 and is pressed against an abutment collar 15 on thebearing shaft 9 by means of a nut 16 screwed onto the upper part of thebearing shaft as seen in FIGS. 3 and 4. The bearing shaft 9 includesbeneath the abutment collar 15 a slightly conical part 17 which fitsinto a central recess or aperture 18 with the same conicity in theroller 2, and the bottom end of the bearing shaft is terminated with acylindrical screw thread as seen in FIGS. 3 and 4. The roller 2 is urgedagainst the underside of the abutment collar on the bearing shaft 9, bytightening a nut 19. As will be seen from FIGS. 3 and 4, the abutmentcollar 15 is thicker than the underside of the attachment sleeve 8.

In order to enable the unit 7 to be attached to the arm 5, an upper part20 of the attachment sleeve 8 has an internal screw thread which enablesthe unit 7 to be screwed onto a corresponding external screw thread onthe arm 5. FIG. 3 shows the unit 7 attached to the arm 5. The directionin which the unit is screwed onto the arm coincides with the directionin which the roller 2 rotates in operation, therewith ensuring that theattachment sleeve will not be unscrewed from the arm 5 as roller 2rotates. Thus, one of the units 7 has a left-hand thread and the other aright-hand thread. The units 7 belonging to respective rollers 1 and 2are of identical construction with the exception of these differentthread directions.

The roller 2 includes a cylindrical recess or aperture 21 which extendsparallel with but eccentrically to the rotational axis of the roller,and also a drainage passage 22 through which coolant sprayed onto theroller during operation is drained-off. The arm 5 also includes air orlubricant passageways 23.

When a rolling mill that includes a roller guide of the aforedescribedkind is operating, the rolled metal that passes through the mill willcause the rollers 1, 2 to rotate together with the bearing shafts 9 andthe inner bearing rings, whereas the attachment sleeves 8 and the outerbearing rings will remain stationary.

The described roller guides are intended for use in the final stages ofa rolling mill and are constructed to permit rolling speeds of up to 170m/sec. Since the rollers then have a diameter of about 45 mm, they willrotate at very high speeds, resulting in bias on the bearings, causingthe bearings to wear rapidly causing subsequent production stoppages inorder to effect a bearing change. It is not unusual for this load biason the bearings to occur because the roller guide grooves are not trulyat right angles to the rotational axis of the rollers, owing to the factthat the axis of the tool that has produced the peripheral guide groovewas not perfectly coaxial with the rotational axis of the rollerbearing.

In order to eliminate this error source, it is proposed in accordancewith the invention that the peripheral guide groove of a roller in aroller guide is formed by rotating the roller in its own bearing, andthe aforedescribed roller guide is constructed to this end.

FIG. 5 illustrates an embodiment of a device for grinding a guide groove24 in the roller 2 of the roller guide described with reference to.

This device includes a holder 25 for a unit 7 comprised of acircumferential roller-guide roller seated in its bearing, wherein theillustrated holder includes an arm which is provided with an externalscrew thread corresponding to the internal screw thread on the upperpart of the attachment sleeve 8. A grinding disc 26 is mounted on theupper side of the arm 25 in

FIG. 5, opposite the cylindrical outer surface of the roller 2 of a unit7 mounted on the arm 25. This grinding disc 26 is rotatable about anaxis that extends parallel with the axis of the arm 25, and thus alsoparallel with the rotational axis of the roller 2. The grinding disc canalso be moved in a direction perpendicular to the axis of the arm 25.Finally, the device also includes means for rotating a fitted roller 2.In the case of the illustrated embodiment, this drive means comprises apin 27 which is rotatable about an axis coinciding with the axis of thearm 25 and is located radially outside its rotational axis at the samedistance therefrom as the distance of the aperture 21 in the roller 2from the rotational axis of said roller, and also has a smaller diameterthan said aperture.

The described device operates as follows:

After having fitted the unit 7 onto the holder 25 and inserted the pin27 into the aperture 21 in the roller, driving of the pin 27 isinitiated and rotation of the grinding disc 26 i started. The grindingdisc and the pin are preferably rotated in different directions,although they may, of course, be rotated in mutually the same directionbut at different speeds. As material is removed from the roller, thegrinding disc is moved radially towards the center of the roller untilthe peripheral groove thus obtained in the roller 2 has received thedesired shape. Air is injected towards the unit 7 through the inlet 28provided in the arm 25, with the intention of avoiding the ingress ofgrinding fragments, dust and other contaminant particles into thebearings. Because the diameter of the hole 21 is larger than thediameter of the pin 27 its rotational axis can be displaced slightly inrelation to the rotational axis of the roller 2 without subjecting theroller to biasing loads.

As will be understood, because the roller 2 rotates in its own bearingwhile being ground, it is ensured that the groove 24 formed in theroller will lie exactly at right angles to the axis around which theroller 2 rotates during a rolling process, and that no biasing forceswill act on the bearings 11, 12 during a rolling process, by virtue ofthe fact that when forming the groove in the roller the roller or thegroove-forming tool rotates about an axis which is slightly inclined tothe axis about which the roller rotates in a mill rolling operation.

It will be understood that the described device is also used to grindthe roller 2 in the aforedescribed manner on subsequent occasions, whenthe groove becomes worn. FIG. 3 illustrates in broken lines the contourof a roller 2 which has been ground down to a maximum.

It will be understood that the described device can be modified withinthe scope of the invention. For instance, the guide roller can berotated by means other than the pin 27, for instance by means of rollerdriving means that are in contact with the outer cylindrical surface ofthe roller 2. Furthermore, the grinding disc may be stationary and thearm 25 and the means for rotating the roller may be movable at rightangles to the rotational axis of the roller. The invention method canalso be applied to other types of rollers with other types of bearings,provided that the roller and its bearing can be removed as a unit fromthe remainder of the roller guide. The invention is therefore restrictedsolely by the contents of the following claims.

What is claimed is:
 1. A method for grinding a circumferential groove inthe periphery of a rolling mill guide roller, said method comprising:a.providing a unit consisting of guide roller and its operating bearingassembly, which as a unit can be readily attached to and removed from arolling mill stand; b. attaching said unit to a support of a grindingdevice that is separate from the rolling mill stand; c. grinding acircumferential groove in the periphery of the guide roller of saidunit, the guide roller being rotatably supported in its operatingbearing assembly.
 2. A method according to claim 1, wherein the step ofgrinding a circumferential groove includes bringing a rotating grindingdisc radially into contact with the periphery of the roller; androtating the roller at a peripheral speed different from the speed atwhich the grinding disc is rotated.
 3. A method according to claim 1,including the step of injecting air under pressure against an innersurface of the roller during the grinding step.
 4. A device for grindingcircumferential grooves in guide rollers of rolling mills while theguide rollers are separated from a rolling mill and are carried on guideroller operating bearing assemblies, said device comprising: a holderfor rotatably supporting a guide roller having a peripheral surface anda guide roller operating bearing assembly so that the guide roller isable to rotate freely about an axis of rotation while carried on itsoperating bearing by the holder, a grinding tool spaced radiallyoutwardly from the guide roller axis of rotation and movable radiallytoward and away from the guide roller peripheral surface while the guideroller is supported by the holder, and roller rotating means forrotating the guide roller about its axis of rotation.
 5. A deviceaccording to claim 4, wherein the guide roller includes a drive aperturespaced from the guide roller axis of rotation, and wherein the rollerrotating means includes a drive pin engageable with the drive aperturefor rotationally driving the guide roller about its axis of rotation. 6.A roller guide for rolling mills, said roller guide comprising: a rollerhaving an axis of rotation, a bearing shaft defining a roller axis ofrotation, a bearing carried by the bearing shaft for rotatablysupporting the roller and bearing shaft for rotation about the rolleraxis of rotation, and an attachment sleeve rotatably carried by thebearing for supporting the roller and bearing shaft, wherein theattachment sleeve includes attachment means for removably attaching theroller and the bearing to a roller holder carried by a rolling mill. 7.A guide according to claim 6, wherein the attachment sleeve includes abearing seat and the attachment means includes an internal screw thread,wherein the bearing includes ball bearings having an outer and an innerbearing ring, and wherein the bearing shaft includes an external screwthread on respective ends thereof and an abutment collar against whichone side of the inner bearing part ring abuts when a opposite side ofthe inner bearing ring is pressed under axial bias by means of a nutscrewed onto one end of the bearing shaft, and against an opposite sideof which abutment collar the roller can be pressed by a nut screwed ontoan opposite end of the bearing pin shaft.
 8. A guide according to claim7, wherein the roller has a cupped shape which includes a cylindricalwall and a bottom wall having a first, central axially extendingaperture and a second axially extending aperture radially spaced fromthe first aperture.
 9. A guide according to claim 6, wherein the bearingincludes two angular contact bearings.
 10. A guide according to claim 8,wherein on end of the bearing shaft tapers conically and wherein thefirst aperture in the roller has a conical shape which is complementarythereto.